Device and method for low-pressure casting of metal melts

ABSTRACT

A device and a method for the low-pressure casting of metal melts, comprising a casting furnace ( 1 ), a feed channel ( 2 ) for the metal melt, a channel ( 4 ) in the direction toward the casting mold ( 5 ), and a feed ( 6 ) for the gaseous pressure application, an intermediate container ( 7 ) being disposed between the casting mold ( 5 ) and the channel ( 4 ), and an access ( 8 ) for adding an inoculating agent ( 9 ) being provided in the intermediate container ( 7 ).

BACKGROUND OF THE INVENTION

The invention relates to a device for the low-pressure casting of metalmelts, comprising a casting furnace, a feed duct for the melt, a duct inthe direction toward the casting mold and a feed for gaseous pressureapplication.

During low-pressure casting, the melt is conveyed via a riser into acasting cavity, counter to the force of gravity, by subjecting themetallic melt to gaseous pressure application in a furnace.

During gravity casting, melts which have additives or inoculants addedto them before the casting for reasons of nucleation are treated beforethey enter the mold in the casting stream, in the tundish and/or in themold itself.

According to the prior art, lumps of inoculant can be introduced, duringthe low-pressure casting, in the region of the mold runner in order todissolve as the mold is filled. The disadvantage frequently associatedwith this is, in particular, that the inoculant in the metal melt is notdistributed in a satisfactory manner in the casting mold. Differentconcentrations of the inoculant in the melt can result in considerabledeviations in the desired properties of the cast pieces. This knowntechnique requires careful adjustment of the composition and of thesolution behavior of the inoculant.

In order to minimize these disadvantages, it is an object of theinvention to use a device and a process for low-pressure casting in sucha way that the melt is already present with a uniformly distributedquantity of inoculant in an intermediate vessel, before the actualfilling of the mold.

SUMMARY OF THE INVENTION

According to the invention, the object is achieved by virtue of the factthat an intermediate vessel is arranged between the casting mold and theduct, an access point being provided in the intermediate vessel for theaddition of an inoculant.

The option of a separate access point for the addition of an inoculantto an intermediate vessel between the casting furnace and the castingmold makes it possible to feed a precisely set quantity of inoculant atthe desired point in time in a simple manner.

According to a preferred embodiment, an overflow wall is arranged insidethe intermediate vessel. It has advantageously been shown that optimumdistribution of the inoculant in the melt, in particular by the flow, isachieved when the inoculant is introduced upstream of the intermediatewall.

Further possible embodiments are described hereinbelow.

BRIEF DESCRIPTION OF THE DRAWINGS

An exemplary embodiment is shown in the drawing.

FIG. 1 shows a sectional view of a furnace.

DETAILED DESCRIPTION

The casting furnace 1 comprises a feed duct 2 for the filling operationwith metal melt 3. The feed duct 2 can be closed by means of a cover 14.A feed 6 is provided on the casting furnace 1 in order to apply gaspressure to the melt. Furthermore, a duct 4 adjoined directly by theintermediate vessel 7 is fitted on the casting furnace 1. The castingmold 5 is arranged above the intermediate vessel 7 and is connected tothe intermediate vessel 7 by way of the riser 13 via the opening 11. Atubular attachment 15 for the addition of the inoculant 9 is fitted atthe access point 8 to the intermediate vessel 7. An overflow wall 10 forthe melt 3 is provided inside the intermediate vessel 7 and is arrangedslightly downstream of the end of the duct 4.

The casting operation proceeds as follows:

First of all, the casting furnace 1 is filled with metal melt 3 via thefeed duct 2. After the casting furnace 1 has been filled, the feed duct2 is closed in a gas-tight manner by means of a cover 14. The pressuresp1, p2 and p3 correspond to atmospheric pressure. For the transport ofiron into the intermediate vessel, the chamber 16 is subjected to theapplication of pressure with a gaseous medium. The pressure p1 isgreater than the pressures p2 and p3. The melt begins to flow into theintermediate vessel 7 via the duct 4 and the overflow wall 10. At thesame time, the inoculant 9 is added via the tubular attachment 15. InFIG. 1, the addition opening is arranged between the overflow wall 10and the casting mold 5. It is likewise conceivable to add the inoculant9 in the region 17, i.e. upstream of the overflow wall 10. The inoculant9 is mixed homogeneously with the metal melt 3 owing to the flow of themetal melt 3. In order to fill the casting mold 5, it is necessary tobuild up the pressure p2, which corresponds to the height ΔH.

After the mold has been filled, p2 is lowered to such an extent that themelt located outside the casting mold can flow back into theintermediate vessel 7.

1-6. (canceled)
 7. An apparatus for the low pressure casting of metalmelts, comprising: a casting furnace having an inlet feed duct, anoutlet duct and a feed for gaseous pressure application; a casting molddownstream of the outlet duct; an intermediate vessel located betweenthe outlet duct and the casting mold; and an access point to theintermediate vessel for the addition of an inoculant to the metal meltin the intermediate vessel.
 8. The apparatus according to claim 7,further including an overflow wall arranged in the intermediate vessel.9. The apparatus according to claim 8, wherein the access point for theinoculant is arranged upstream of the overflow wall.
 10. The apparatusaccording to claim 7, wherein the intermediate vessel has an opening anda riser is arranged inside the intermediate vessel at the opening andthe casting mold is connected directly to the riser above the opening.11. A process for the low pressure casting of metal melts, comprising:providing a casting furnace having an inlet feed duct, an outlet ductand a feed for gaseous pressure application; providing a casting molddownstream of the outlet duct; providing an intermediate vessel locatedbetween the outlet duct and the casting mold; providing an access pointto the intermediate vessel for the addition of an inoculant to the metalmelt in the intermediate vessel; and introducing an inoculant into themetal melt in the intermediate vessel through the access point.
 12. Theprocess as claimed in claim 11, including adding the inoculant in theform of granules.